Serologic Testing For Syphilis With Traditional And .

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Serologic Testing for Syphilis with Traditionaland Reverse AlgorithmsSean Schafer, MD MPHMedical EpidemiologistHIV/STD/TB SectionOregon Public Health Division

You’ll leave knowing something about “Treponemal” and “non-treponemal” tests forsyphilis “Traditional” and “reverse syphilis” screening Rapid diagnostic tests for syphilis

Outline Syphilis Causative agent Key facts about syphilis Laboratory tests for diagnosis of syphilis Non-treponemal tests Treponemal tests Traditional algorithm for syphilis screening Reverse algorithm for syphilis screening Interpretation and follow-up New rapid diagnostic test for syphilis

Attribution:Many slides adapted from ES Theel. Serologic Testing for Syphilis: comparison ofthe Traditional and Reverse Screening Algorithms.Mayo Clinic, Rochester, Minnesota. October 24, 2012Available s.ppt. Accessed May 16, 2015

Rates of early syphilis by sex and year—Oregon, 2000–2015Men19.3*Overall10.6*Women2.0**for 10 months .will be higher by 25–30%Year

Treponema pallidum Bacterium “Spirochete” Motile (“corkscrew”) Can’t culture in lab Transmission Sexual Trans-placental Percutaneous following contact with infectiouslesions Bloodborn Extremely rarewadsworth.org

Spirochaete Spirochaetaceae Treponema pallidum (syphilis, yaws), carateum (pinta),denticola Borrelia burgdorferii/afzelii (lyme),hermsii/duttoni/parkeri (tick-bornerelapsing fever) Leptospiraceae Leptospira interrogans (leptospirosis) Spirillaceae Spirillium minus (rat-bite fever)

Syphilis—a few key concepts Highly infectious Infectious Dose 57 organisms Attack rate 1/3 Incubation – 21 days (median) 3 clinical stages Primary: Painless sore (chancre) at inoculation site Secondary: Rash, fever, lymphadenopathy, malaise Symptomatic Late/Tertiary: Dementia, tabes dorsalis, cardiovascular disease

Lab Diagnosis—uncommon methodshttp://www.els.netRabbit Infectivity Test (RIT)Dark field microscopyImmunostainingCDC/NCHSTP/Dividion of STD Preventiontextbookofbacteriology.netPolymerase Chain Reaction (PCR)

Lab Diagnosis—common methods Serology (tests for antibodies producedupon syphilis infection) Mainstay for syphilis testing Two kinds Non-treponemal Treponemal

Non-treponemal serologic tests T. pallidum causes cells to release cardiolipin Reagin antibody to cardiolipin Non-treponemal tests measure levels of reagin: Rapid Plasma Reagin (RPR) Venereal Disease Research Laboratory (VDRL) Toluidine red unheated serum test (TRUST)

RPR and VDRL are agglutination assays Reagent is carbon particles cardiolipin No reagin present, no agglutinationCharcoalCardiolipin

Reagin present .agglutination ofthe charcoalReagin

Non-Treponemal Test Advantages Rapid turnaround time – minutes Inexpensive No specialized instrumentation required Usually revert to negative following therapy Can be used to monitor response to therapy12

Non-Treponemal Test Limitations Results are subjective Intra- and Inter-laboratory variability False positives (lower specficity) lupus, pregnancy, viral hepatitis Might be negative (lower sensitivity) in veryearly syphilis and late syphilis even if nevertreated Low “throughput” can’t be “batched”

Treponemal serologic tests Syphilis Antibodies against T. pallidum Tests detect ‘treponeme specific’ antibodies Fluorescent treponemal antibody absorbtion test (FTA-ABS)Microhemagglutination assay (MHA)T. pallidum particle agglutination (TP-PA)Enzyme Immunoassay (EIA)Immunochromatographic strips (ICS point of care tests)FTA-ABSICS

Treponemal Test Advantages Few false positives (high specificity) Fewer false negatives (more sensitive)especially during early and late syphilis Objective result interpretation Automation option High throughput “batchable” High reproducibility/precision

Treponemal Test Limitations Remain positive for life Cannot be used to monitor response to therapy Conventional (older) versions (e.g. FTA-ABS, TP-PA) Subjective interpretation like non-treponemal tests Newer versions Expensive instrumentation Higher cost/test

Syphilis Screening Algorithms:Traditional versus ‘Reverse’

Traditional AlgorithmNon-treponemal test (e.g., RPR)ReactiveNon-reactiveTreponemal test (e.g., FTA)ReactiveSyphilisNon-reactiveNot syphilisNot syphilis

Traditional algorithm pros and cons Pros Familiar One confirmation test, typically done reflexively, leadsto clear result Rapid, inexpensive Recommended by CDC Cons Manual Subjective interpretation False-positives False negatives, especially late syphilis

Reverse AlgorithmTreponemal test (eg, EIA)ReactiveNon-reactiveNon-Treponemal test (eg, RPR)ReactiveSyphilisNot syphilisNon-reactiveSecond Treponemal Test (e.g., FTA)ReactiveProbably syphilisNon-reactiveNot syphilis

Reverse algorithm pros and cons Pros Objective Can be batched for high volume labs Recommended by public health agencies in Europe andCanada More sensitive and more specific more cases of syphilisdiagnosed and treated Cons Unfamiliar Cost Complexity – often second confirmatory test needed, notyet typically done reflexively Disfavored by CDC

Interpreting reverse algorithmCase #1 37-year-old man with HIV 2-weeks of fatigue, fever and rash on palms andsoles Previously resolved genital lesion Syphilis IgG by EIA: positive RPR: positive, titer of 1:64

Interpreting reverse algorithmCase #1 Conclusion Untreated or recently treated syphilis Follow treatment guidelines No further testing needed on this sample For follow-up after treatment RPR titers only, should fall 4-fold (2dilutions, e.g. 1:64 to 1:16)

Interpreting reverse algorithmCase #2 23-year-old female First-trimester pregnancy screening Previously healthy Syphilis IgG by EIA: positive RPR: negative Second treponemal test, FTA: negative

Interpreting reverse algorithmCase #2 conclusion False positive EIA Not syphilis No further screening at this time Consider screening again at 28 weeks anddelivery if syphilis prevalent in community

Interpreting reverse algorithmCase #3 50-year-old Somalian immigrant Kidney transplant evaluation No known history of syphilis or treatment Syphilis IgG by EIA: positive RPR: negative FTA: positive

Interpreting reverse algorithmCase #3 Conclusion Possible latent syphilis Evaluate and treat according to current guidelines Consider lumbar puncture if neurologicsymptoms consistent with late neurosyphilis

Interpreting reverse algorithmCase #4 30-year-old inmate Past history of treated syphilis (10 years prior) Syphilis IgG by EIA: positive RPR: negative

Interpreting reverse algorithmCase #4 Conclusion Consistent with successfully treated syphilis No additional testing needed

Summary Syphilis usually diagnosed by serology Non-treponemal (e.g., RPR, VDRL) Treponemal (e.g., FTA, TP-PA, EIA, MFI) Traditional Algorithm Non-treponemal test (RPR) first Treponemal test to confirm Advantages Recommended by CDC Cost-effective Suitable for most lower throughput labs Limitations May miss very early or late/latent infection

Summary Reverse Algorithm Treponemal test first Confirm with RPR If RPR negative, use different treponemal‘tiebreaker’ test Advantages High volume throughput More sensitive, same specificity Limitations Result interpretation can be challenging ‘Tiebreaker’ test not yet reflexive in most labs

Reverse algorithm pros and cons Pros Objective Can be batched for high volume labs Recommended by public health agencies in Europe and Canada More sensitive and more specific more cases of syphilis diagnosed and treated Cons Unfamiliar Cost Complexity –often second con

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